Rewritten the telemetry handling code

The new code reflects the latest discussions of the openLRSng's
telemetry implementation:
- We try to keep each frame under 9 bytes including header due to
timming limits.
- Frame contents changed as we now have a well defined range for sensors
(0x40 to 0x7f).
- Frame size is now dynamic when receiving (telemetry.h line 104-406) vs
previous version where it was 11 bytes static.
- Added a handicap to telemetry_type::updated() this will avoid from
chattier sensors always filling the queue.
- telemetry_class::transmit() now only allows sending one frame at each
call.
- Added some new classes, check telemetry_type.h.